The present invention is directed to an infusion pump tube for use in a positive displacement infusion pump.
Positive displacement pumps for the infusion of parenteral medical fluids are generally characterized by a length of flexible tubing which is acted upon by one or more pumping elements. A rotary mechanism such as a cam shaft is generally used to reciprocate the pumping elements. The flexible tubing is generally disposed between the pumping elements and an opposing platen. The particular infusion pump described herein utilizes two valves and an expulsor as the pumping elements.
One valve serves as an inlet and the other as an outlet. The expulsor serves to compress the flexible infusion pump tube and expel fluid. When the expulsor is retracted from the pump tube, the tube returns to its substantially round uncompressed position. In operation, the inlet valve opens to allow fluid into the tube with the expulsor retracted. To expel fluid, the inlet valve closes, the outlet valve opens and the expulsor is moved against the tube to fully compress it.
An important factor in the accuracy of the fluid delivered by such a pump is the dimension of the infusion pump tube which is acted upon by the expulsor. The volume of fluid expelled by the expulsor is closely approximate to the area of the substantially round internal passageway of the pump tube times the length of the expulsor. Thus, any variation in the manufacturing process which affects the area of the substantially round internal passageway of the tube will affect the volume of fluid expelled. Furthermore, mounting of the tube within the pump in a manner which varies the stretching of the tube from pump to pump will also affect the effective area of the internal passageway thereby affecting the volume of fluid expelled.
A method of mounting a pump tube within an infusion pump is disclosed in U.S. Pat. No. 5,011,378 (Brown et al.). Brown et al. discloses a pump tube mount with a cylindrical fitting having an annular groove around its exterior surface. A pump tube mounted on this fitting is held in place by a collar placed over the tube concentrically aligned with the groove. The pump tube mount includes a rear wall with a pair of tabs for holding the mount in place within an infusion pump.
The object of the present invention is to start with a precisely manufactured tube and mount it into an infusion pump in a manner such that the dimensions of the tube are repeatable.